Active matrix substrate with height control member

ABSTRACT

An active matrix substrate comprises a substrate, a plurality of adhesion parts provided on the substrate so as to have substantially the same height, and a plurality of active elements provided on the plurality of adhesion parts, respectively, each of the plurality of adhesion parts including a height control member and an adhesive.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/187,015, filed Jul. 2, 2002, and is based upon and claims the benefitof priority from the prior Japanese Patent Application No. 2001-208723,filed Jul. 10, 2001, the entire contents of each of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to active matrix substrates and a method ofmanufacturing active matrix substrates.

2. Description of the Related Art

An active matrix display where an active element is provided for eachpixel can realize a flat-type display with high picture quality. Ofdisplays of this type, a liquid-crystal display (LCD) that uses liquidcrystal as an optical shutter and drives each pixel with an activeelement, such as a TFT, has been widely used.

A known organic electroluminescence (EL) display is such that ELmaterial capable of emitting red, green, and blue (RGB) light is formedby inkjet techniques and mask deposition techniques to make pixels, andeach pixel is driven by an active element, such as a TFT. The organic ELdisplay can also display a full color image on a thin panel screen.

In the prior art, to form the pixel section of such an active matrixflat-type display, each component layer is formed on a glass substrateusing vacuum thin layer processes, such as CVD or sputtering techniques.The layers are then subjected to microscopic processing by dry etchingor wet etching and by photolithography. These processes are repeated foreach of the layers, including a semiconductor layer, an electrode layermade of metal or the like, and an insulating layer. As a result, thenumber of processes increases, resulting in an increase in the cost.

In the flat-type display, the active elements are formed not on theentire surface of the substrate but on a part of each pixel. Thus, it isa waste of time and labor to form all the active elements provided onthe glass substrate. Such a wasteful forming method sets the economicallimits to the formation of a large-area display.

In contrast, one known method is such that a plurality of activeelements are formed very densely beforehand on an element formationsubstrate and that they are transferred to an intermediate substrate andfurther transferred to a display substrate (or a final substrate), andthereafter, passive structures, including interconnections and pixelelectrodes, are formed, thereby reducing the cost (for example, refer toJpn. Pat. Appln. KOKAI Publication No. 2001-7340).

FIG. 1 shows part of the process of transferring active elements from anintermediate substrate to a final substrate in Jpn. Pat. Appln. KOKAIPublication No. 2001-7340. As shown in FIG. 1, on a final substrate2501, patterned scanning lines 2503, interlayer insulators 2504,patterned signal lines 2502, a planarization layer 2505 are stacked oneon top of another in this order. On the planarization layer 2505, anadhesion layer 2506 is provided. In the interlayer insulators 2504 andplanarization layer 2505, contact holes for subsequent wiring are madein the areas corresponding to the signal lines 2502 and scanning lines2503.

At the intermediate substrate 2507, TFTs 2510 are formed via a temporaryadhesion layer 2508. The TFTs 2510 are covered with a protective layer2509. At the bottom of each of the TFTs 2510, an under layer 2511 isprovided to protect the TFT.

To transfer the TFTs 2510 from the intermediate substrate 2507 to thefinal substrate 2501, the TFTs 2510 to be transferred are aligned withthe adhesion layer 2506. Then, light is projected through a shading mask2512 which has an opening only in this area. Then, the adhesion of thetemporary adhesion layer 2508 is weakened and the under layer 2511 isbonded to the adhesion layer 2506, thereby performing transfer.

In this method, TFTs 2510 requiring many manufacturing processes areformed on the element formation substrate with a high element density.The TFTs 2510 are transferred once from the element formation substrateto the intermediate substrate 2507. Then, the TFTs 2510 on theintermediate substrate 2507 are further transferred onto the finalsubstrate 2501. At that time, use of a large element formation substrateand a large intermediate substrate 2507 enables TFTs 2510 arranged witha high density to be selected at regular intervals and transferred tothe final substrate 2501 by way of the intermediate substrate. Usingsuch a method makes it possible for TFTs 2510 used for many substratesto be formed on a single element formation substrate, which reduces thecost equivalent to the ratio of the TFT density of the element formationsubstrate to that of the final substrate.

When the TFTs 2510 are transferred to the final substrate 2501 by themethod shown in FIG. 1, the TFTs 2510 are pressed against the adhesionlayer 2506. In this case, it is difficult to control the force withwhich the TFTs 2510 are pressed. When the adhesion layer is pressed, thefollowing problem arises: the height of the adhesion layer 2506 spreadsideways differs from that of the adhesion layer 2506 not spread or theTFTs 2510 are not in parallel with the final substrate. Since the heightof the TFTs 2510 provided on the final substrate 2501 and the angle ofthe TFTs 2510 with the final substrate 2510 are not controlled, theformation of interconnections after the TFTs 2510 are formed isdifficult.

Furthermore, when the TFTS 2510 are pressed against the adhesion layer2506 for transfer, there is a possibility that the adhesion layer 2506will spread sideways and the adjacent TFTs 2510 also adhere to theadhesion layer 2506. Therefore, to prevent the adjacent TFTs 2510 fromadhering to the adhesion layer 2506 even when the adhesion layer 2506spreads sideways, the adjacent TFTs 2510 have to be spaced a suitabledistance apart from each other. As a result, the number of TFTs 2510formed on a single element formation substrate decreases, which causesthe problem of increasing the cost.

Therefore, there has been a need to realize an active matrix substratewhich is capable of controlling the height of active elements from thesurface of the final substrate in transferring the active elements andthat enables the active elements to be almost parallel with the finalsubstrate even via an adhesion layer, and a method of manufacturing suchactive matrix substrates.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is providedan active matrix substrate comprising a substrate; a plurality ofadhesion parts provided on the substrate having substantially the sameheight, each of the plurality of adhesion parts including a heightcontrol member and an adhesive; and a plurality of active elementsprovided on the plurality of adhesion parts.

According to a second aspect of the present invention, there is provideda method of manufacturing an active matrix substrate, comprising forminga plurality of active elements on a first substrate; forming a pluralityof adhesion parts on a second substrate, each of the adhesion partsincluding an adhesive and a height control member surrounding theadhesive; selectively transferring the plurality of active elements tothe second substrate in such a manner that the plurality of activeelements adhere to the adhesion parts; and forming interconnectionsbetween the plurality of active elements transferred onto the secondsubstrate.

According to a third aspect of the present invention, there is provideda method of manufacturing an active matrix substrate, comprising forminga plurality of active elements on a first substrate; forming a pluralityof adhesion parts on a second substrate, each of the plurality ofadhesion parts including a plurality of height control members in anadhesive; selectively transferring the plurality of active elements tothe second substrate in such a manner that the plurality of activeelements adhere to the plurality of adhesion parts; and forminginterconnections between the plurality of active elements transferredonto the second substrate.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a sectional view to help explain the element transferringprocess in a conventional active matrix substrate manufacturing method;

FIG. 2 is a sectional view to help explain the element forming processin an active matrix substrate manufacturing method according to a firstembodiment of the present invention;

FIG. 3A is a sectional view to help explain the temporary adhesionprocess for an element formation substrate and an intermediate substratein the first embodiment;

FIGS. 3B to 3D are sectional views to help explain modifications of theprocess of FIG. 3A;

FIG. 4 is a sectional view to help explain the state after the transferto the intermediate substrate has been completed in the firstembodiment;

FIGS. 5 and 6 are sectional views to help explain the process of formingan adhesion part on a final substrate in the first embodiment;

FIG. 7 is a plan view corresponding to the process of FIG. 6;

FIGS. 8 and 9 are sectional views to help explain the adhesion processfor the intermediate substrate and final substrate in the firstembodiment;

FIG. 10 is a plan view to help explain how the adhesion part and anactive element are laid on top of the other in the process of FIG. 9;

FIG. 11 is a sectional view to help explain the state where the transferof the active elements to the final substrate has been completed in thefirst embodiment;

FIGS. 12 and 13 are sectional views to help explain the process offorming interconnections on the final substrate in the first embodiment;

FIG. 14 is a circuit diagram of one pixel in an organic EL displayaccording to a second embodiment;

FIG. 15 is a plan view of one pixel in the organic EL display accordingto the second embodiment;

FIG. 16 is a plan view of the active element for one pixel in theorganic EL display according to the second embodiment;

FIG. 17 is a sectional view taken along line 17-17 of FIG. 16;

FIG. 18 is a sectional view to help explain a modification of theadhesion process for the intermediate substrate and the final substrate(see FIG. 9) in the first or second embodiment;

FIGS. 19A and 19B are a sectional view and a plan view to help explainthe way an adhesion part and an active element are laid one on top ofthe other in the process of manufacturing active matrix substratesaccording to a third embodiment;

FIGS. 20A and 20B are a sectional view and a plan view to help explainthe way the adhesion part and the active element are laid one on top ofthe other in the process of manufacturing active matrix substratesaccording to the fourth embodiment;

FIG. 20C is a plan view of an active element to help explain an exampleof the arrangement of contact sections of the active element suitablefor the configuration of FIG. 20B;

FIGS. 21A and 21B are a sectional view and a plan view to help explainthe way an adhesion part and an active element are laid one on top ofthe other in an active matrix substrate manufacturing method accordingto a fifth embodiment of the present invention;

FIGS. 22A and 22B are a sectional view and a plan view which helpexplain the way an adhesion part and an active element are laid one ontop of the other in an active matrix substrate manufacturing methodaccording to a sixth embodiment and which illustrate an example offurther providing a plurality of parallel height control members underthe active element;

FIGS. 23A and 23B are a sectional view and a plan view which helpexplain the way an adhesion part and an active element are laid one ontop of the other in an active matrix substrate manufacturing methodaccording to a seventh embodiment and which correspond to an example ofeliminating the cylindrical height control members from the sixthembodiment;

FIGS. 24A and 24B are a sectional view and a plan view which helpexplain the way an adhesion part and an active element are laid one ontop of the other in an active matrix substrate manufacturing methodaccording to an eighth embodiment and which illustrate an example ofdistributing height control members in an adhesive; and

FIGS. 25A and 25B are a sectional view and a plan view which helpexplain the way an adhesion part and an active element are laid one ontop of the other in an active matrix substrate manufacturing methodaccording to a ninth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, referring to the accompanying drawings, embodiments of thepresent invention will be explained.

First Embodiment

In a first embodiment of the present invention, active elements(hereinafter, referred to as elements) are formed at an elementformation substrate (a first substrate) and transferred to anintermediate substrate. Then, they are further transferred to a finalsubstrate (a second substrate) at which a height control member and anadhesive surrounded (enclosed) by the height control member have beenformed, thereafter forming interconnections and others, which completesan active matrix substrate. The height control member makes the heightsof the adhesion parts at a certain height. A sectional view of a part ofan active matrix substrate according to the first embodiment is shown inFIG. 13. The configuration of the active matrix substrate will beexplained by reference to FIG. 13.

The active matrix substrate of the first embodiment has adhesion parts404 provided so as to have practically the same height as that of thefinal substrate 401 and elements 301 provided on the adhesion parts 404.Each of the adhesion parts 404 includes an adhesive 403 and a heightcontrol member 402 provided so as to surround the adhesive 403. Apost-transfer insulating layer 415 is provided on the entire surface ofeach of the elements 301. An opening is made in the post-transferinsulating layer 415 in the area corresponding to the contact section ofeach element 301. Then, conducting layers and interconnections, such aspixel electrodes 201 to be connected to the elements 301, are formed.

Hereinafter, a method of manufacturing the active matrix substrate willbe explained. First, a method of forming elements on an elementformation substrate and transferring the elements to an intermediatesubstrate (a third substrate) will be explained by reference to FIGS. 2to 4.

First, as shown in FIG. 2, elements 301 are formed on an elementformation substrate 501. An element 301 may be a single TFT or a circuitcomposed of a plurality of TFTs. This type of circuit includes anin-pixel memory circuit or a circuit that compensates for variations inthe Vth of the driving TFTs in an organic EL display using four or moreTFTs.

Next, as shown in FIG. 3A, an optical conversion material 602 is formedin the position corresponding to each element 301 on an intermediatesubstrate made of a transparent material, such as glass, by using CrOx,or the like, whose back is blackened. Nitto Denko CorporationRiba-alpha, a tackiness agent which foams by heating to decrease inadhesion and is used as a temporary adhesion layer 603, is applied tothe intermediate substrate 601 on which the optical conversion material602 has been formed to a thickness of about 5 to 20 μm. Then, theresulting layer is laminated with the element formation substrate 501under vacuum.

In this embodiment, infrared rays, visible rays, or the like areprojected so as to be absorbed by the optical conversion material 602,which converts the rays of light into heat. As a result, the temporaryadhesion layer 603 is heated and therefore foams, which decreases theadhesion. Therefore, what is obtained by patterning a metal layer, madeof CrOx, MoTa, MoW, TiOx, or the like, with its light-projected surfacebeing blackened, or a multilayer film of these layers, a carbon layer, ablack organic paint layer, or the like may be used as the opticalconversion material 602.

In a case where a material that comes off when light, such asultraviolet light, not heat, is projected on the material is used as thetemporary adhesion layer 603, what is obtained by patterning a materialthat converts the wavelength of the projected light into a wavelengththat promotes the detachment is used as the optical conversion material602. When the distance between the elements 301 is fine, the opticalconversion material 602 is effective in increasing the selectingresolution of elements 301. When the distance between the elements 301is coarse and the peel strength of the temporary adhesion layer isproperly controlled, the optical conversion material 602 may beeliminated as shown in FIG. 3B As shown in FIG. 3C, the opticalconversion material 604 may be formed on the element 301. In that case,an insulating black resin about 1 to 3 μm thick in which pigment hasbeen dispersed may be formed on the top surface of the element as partof a protective layer. Providing the optical conversion material 604 onthe element 301 allows the element 301 itself to generate heat. Thisenables the heating area to be localized, which increases remarkably theresolution in peeling the temporary adhesion layer 603. For example, ina case where the dimension of the element is about 50 μm and thedistance between elements is about 5 to 10 μm, the temporary adhesionlayer 603 can be peeled without any problem.

Furthermore, the temporary adhesion layer 603 may adhere to an uppersurface of the element 301, as shown in FIG. 3D. When the temporaryadhesive layer is a tackiness agent layer formed on the intermediatelayer 601 or a tackiness tape, it suffices that the temporary adhesivelayer may be pressed to the element 301 to achieve a construction shownin FIG. 3D. The element 301 may include the optical conversion material604 shown in FIG. 3C.

A sheet-like material which is obtained by applying a tackiness agentthat is adhesive and can decrease the tackiness by heat or light to acarrier film may be used as the temporary adhesion layer 603. Thismaterial is effective especially in the case where the opticalconversion material 604 is provided on the element 301. The reason isthat providing the optical conversion material 604 on the element 301makes it possible to increase the resolution in peeling the temporaryadhesion layer 603, even when the carrier film is about 100 μm and thetackiness agent is as thick as about 50 μm.

The optical conversion material 604 provided on the element 301 acts asan opaque layer for the TFT in the element 301 and has the effect ofreducing the optical leakage current. All of the protective layer 414for the element 301 may be made of a black resin. It may be made of amaterial that is not black but absorbs the projected light and convertsit into heat.

The temporary adhesion layer 603 is not limited to the aforementionedmaterial. For instance, Apeazon wax from Apeazon Products Limited, whichdecreases in viscosity and lowers in adhesion when being heated may beused as the temporary adhesion layer 603.

An organic resin material that achieves adhesion by dispersingultraviolet-curing resin into a tackiness agent and decreases theadhesion by hardening the network including the tackiness agent whenbeing struck by light may be used as a material whose adhesiondecreases, reacting with ultraviolet light. A material whose adhesiondecreases with ultraviolet light, such as an acrylic tackiness agentincluding benzophenone apt to resolve with ultraviolet light, may beused.

Furthermore, a heat-sensitive tackiness agent that reacts withtemperature change or adhesive tape may be used as the temporaryadhesion layer 603. For example, use of an organic material that variesbetween the crystalline state and the amorphous state depending ontemperature enables the adhesion to be changed as much as one order ofmagnitude or more. Specifically, Interlimer (a registered trademark ofLandec Corporation) from Nitta Corporation may be used. Although theWarm-Off type that comes off at a temperature higher than the switchingtemperature is easy to use, the Cool-Off type that comes off at atemperature lower than the switching temperature may be used, providedthat the processes are designed for this type. Since the transitionbetween the crystalline and amorphous states is reversible, the materialcan be used a plurality of times.

Not only glass but also a plastic substrate, such as PET or polyolefin,may be used as the intermediate substrate 601. A sheet-like temporaryadhesion layer 603 or a tape-like temporary adhesion layer 603 where anadhesive is coated on a carrier film may be sandwiched and laminatedbetween the intermediate substrate 601 and the element formationsubstrate 501. The temporary adhesion layer 603 may be formed byapplying it to the interlayer substrate 601.

Next, as shown in FIG. 4, the element formation substrate 501 isremoved. In the first embodiment, because the element formationsubstrate 501 is a glass substrate, it is made thinner by mechanicalgrinding and then etched with a mixture of hydrofluoric acid andsurfactant. At this time, to prevent the under layer from being etched,the etching solution and the material of the under layer are adjusted.For example, when glass is etched with fluoric acid etchant, it isdesirable that a fluoric-acid-resistant material, such as AlOx, TaOx,SiNx, or organic resin, should be used as the under layer.

The element formation substrate 501 may be removed not only by grindingor etching but also by making the layer subjected to laser abrasion apart of the under layer or providing this layer under the under layerand projecting a laser beam from the back to peel the substrate 501.

Next, using FIGS. 5 to 13, the process of further transferring theelements transferred to the intermediate substrate to the finalsubstrate and forming interconnections will be explained.

First, as shown in FIG. 5, a height control member 402 is formed in anarea in which the elements are to be transferred on the final substrate401 made of alkali-free glass, soda-lime, plastic, or metal foil. In thefirst embodiment, the height control member 402 is obtained by applyingphotosensitive acrylic resin and patterning the resulting layer byphotolithography. The height control member 402 looks like a ring (bank)that supports the element and is about 1 to 5 μm higher than the finalsubstrate 401. The internal circumference of the height control member402 is made smaller than the size of the element.

The height control member may be formed as high as 1 to 20 μm. If theheight is set in a higher side, needed are prevention measures for astep breakage of interconnections, which is apt to happen at the laterinterconnection formation process. However, thick printing ofinterconnections may overcome this problem when a pixel pitch is coarse.

Next, as shown in FIG. 6, an adhesive 403 is applied inside the heightcontrol member 402 and acts as an adhesion part 404. The adhesive 403 isapplied by screen-printing an ultraviolet-curing adhesive. As shown inFIG. 7, since the height control member 402 surrounds the adhesive 403,the adhesive 403 may be liquid when being applied and be droppedsuitably and then hardened later.

Note that the adhesive applying method is not limited toscreen-printing, but an ink-jet method or a dispensing method may beused to selectively drop the adhesive.

Next, as shown in FIG. 8, the intermediate substrate 601 to which theelements 301 have been transferred is aligned with the final substrate401 on which the adhesion parts 404 have been formed and secured to thelatter temporarily. At this time, the intermediate substrate 601 ispressed against the final substrate 401. The height control member 402has the function of maintaining the height of the adhesion part 404.That is, although the adhesive 403 spreads as a result of being pressedby the bottom surface of the element 301, the existence of the heightcontrol member 402 maintains the height, thereby preventing the adhesive403 from spreading. As a result, the height of the adhesion part 404 iscontrolled to a specific height of the height control member 402. Theamount of the adhesive 403 is large enough to bond the element 301.

The adhesion part 404 is enclosed by the height control member 402,which prevents the part 404 from spreading outward. As a result, asingle element 301 is bonded to a single adhesion part 404 without beingbonded to the area of an adjacent element 301.

When the intermediate substrate 601 is secured temporarily to the finalsubstrate 401, they may be fixed mechanically or bonded with a suitabletemporary fixing adhesive. In the case where fixing is done with thetemporary fixing adhesive, it is desirable that the size of the finalsubstrate 401 should be almost the same as that of the intermediatesubstrate 601 and that the portion fixed with the adhesive should be theperipheral parts of both substrates where there is no element.

Next, as shown in FIG. 9, infrared rays are projected from under theback of the intermediate substrate 601 so that the elements may beselectively peeled from the intermediate substrate 601, thereby reducingthe adhesion of the temporary adhesion layer 603 with which the elements301 to be transferred are secured. At this time, to prevent infraredrays from striking the elements 301 not to be transferred, a glass mask1201 is provided, which causes infrared rays to be selectivelyprojected.

When the temporary adhesion layer 603 has been adjusted so that thelayer 603 may start to peel at about 90° C., the intensity of theinfrared rays is adjusted in such a manner that the optical conversionmaterial 602 of the selected element 301 stays at the peak of at about100° C. for about two seconds. Then, since infrared rays are hardlyprojected onto the unselected elements 301 in the periphery, atemperature of about 80° C. or below can be maintained, resulting inalmost no decrease in the adhesion of the temporary adhesion layer 603securing these elements 301.

At the same time or before the adhesion of the temporary adhesion layer603 is reduced, ultraviolet rays are projected from under the back ofthe final substrate 401 to harden the adhesive 403, thereby bonding theelement 301 to the final substrate 401. At this time, as shown in FIG.10, when the periphery (broken-line section) of the element 301 isprovided further inside the periphery of the height control member 402and the adhesive 403 is provided inside the height control member 402,the step produced from the configuration becomes smooth. Therefore, suchfailures as step breakages or cavities are reduced in subsequent wiring,which improves remarkably the yield of active matrix substrates each ofwhich has as many as more than about one million elements. When theadhesive 403 is of the thermosetting type, the intermediate substrate601 and final substrate 401 may be sandwiched between heating rollers toheat them locally.

The dimensions of each layer in the configuration of FIG. 9 are shown atleft in the figure.

Next, as shown in FIG. 11, in a state where the adhesion of thetemporary adhesion layer 603 is weakened and the adhesive 403 ishardened, the intermediate substrate is separated from the finalsubstrate 401, thereby transferring only specific elements 301 to thefinal substrate 401.

At this time, the adhesive 403 does not adhere to the elements 301excluding the selected elements 301, with the result that one element301 adheres to one adhesion part 404 with an almost 100% selectivity.There is no damage to the untransferred elements remaining on theintermediate substrate 601.

Next, as shown in FIG. 12, on the entire surface of the final substrate401 to which the elements 301 have been transferred, a post-transferinsulating layer (or post-transfer insulator) 415 is formed usingphotosensitive acrylic resin. Openings 108 are made in the post-transferinsulator 415 areas corresponding to the contact sections 108 of theelements 301.

Next, as shown in FIG. 13, Al, ITO (Indium Tin Oxide), or the like isformed all over the surface by sputtering techniques and then patternedto form signal lines, scanning lines, and such wires as pixelelectrodes. This completes an active matrix substrate. In FIG. 13, onlya pixel electrode 201 is shown.

In the first embodiment, the adhesion parts, each including the heightcontrol member and the adhesive surrounded by the height control member,are formed on the final substrate. Onto the adhesion parts, the elementsare transferred. The adhesive does not go over each height controlmember because it is surrounded by the height control member of a ringshape. Therefore, this prevents the adhesive from spreading so much thatadjacent elements are also bonded to one adhesion part at the same timeand transferred to the final substrate.

The height control member may take any shape, provided that it surroundsthe adhesive. The shapes of the outside and inside of the height controlmember are not limited to those in the first embodiment. For instance,they may take the form of a quadrangle, such as a regular square or arectangle, or a circle, or an oval. Since the height of the heightcontrol member in each adhesion part is made almost equal, the height ofthe element on the final substrate is prevented from differing from oneelement to another and the surface of the final substrate is alwaysparallel with the elements, which makes subsequent wiring easy.

It is desirable that the height control members and adhesive should besolid when the active matrix substrate is completed. Since the adhesivedoes not control the height, it may be a solid that has viscosity andfurther plasticity and elasticity.

Second Embodiment

In a second embodiment of the present invention, a method ofmanufacturing displays (or active matrix substrates) by an elementtransferring method according to the first embodiment will be explained.In the second embodiment, two TFTs and a storage capacitor are formed asan element on an element formation substrate. Then, they are transferredto an intermediate substrate and further to a final substrate.Thereafter, inter-connections are formed on the final substrate, therebyforming an EL display.

FIG. 14 is a circuit diagram of a single pixel in the EL display. FIG.15 is a plan view of a pixel. FIG. 16 is a plan view of an element inone pixel (the part enclosed by a dotted line in the figure) in thesingle pixel. FIG. 17 is a sectional view taken along line 17-17 of FIG.16. The part corresponding to the element in FIG. 15 represents theupper interconnections above the element. Since the entire diagram ofthe EL display is such that pixels of this type are arranged in anarray, it will not be given here.

First, using FIG. 14, a circuit of one pixel in the EL display of thesecond embodiment will be explained. One pixel in the EL display of thesecond embodiment comprises a signal line 101, a scanning line 102, ascanning TFT 103, a storage capacitor 104, a driving TFT 105, an organicEL section 106, and a power supply line 107. Terminals 108 in FIG. 14correspond to contact sections 108 in the FIGS. 15 and 16.

The gate of the scanning TFT 103 is connected to the scanning line 102.One of the source and drain of the TFT 103 is connected to the signalline 101 and the other is connected to one electrode of the storagecapacitor 104 and to the gate of the driving TFT 105. The otherelectrode of the storage capacitor 104 is connected to the power supplyline 107. One of the source and drain of the driving TFT 105 isconnected to the power supply line 107 and the other is connected to theorganic EL section 106.

With this pixel, to cause the organic EL section 106 to emit light, apulse on the scanning line 102 turns on the scanning TFT 103 with aspecific timing, thereby applying the image signal from the signal line101 via the scanning TFT 103 to the gate of the driving TFT 105. Thestorage capacitor 104 intervenes between the gate of the driving TFT 105and the power supply line 107. Therefore, charges are prevented fromescaping even after the scanning line goes low and therefore the signalline 101 is separated from the driving transistor 105. As a result,according to the image signal written in the driving transistor 105, thecurrent from the power supply line 107 is supplied to the organic ELsection 106, causing the organic EL section 106 to emit light with aspecific luminance.

A configuration realizing the circuit of FIG. 14 will be explained byreference to FIGS. 15 to 17.

As shown in FIG. 17, an adhesion part 404 which includes a heightcontrol member 402 and an adhesive 403 enclosed by the height controlmember 402 is provided on the final substrate 401. On the adhesion part404, an under layer 405 and a buffer layer 406 are stacked.

On the buffer layer 406, a semiconductor layer 407 of the scanning TFT103 and driving TFT 105 is provided in a specific position. On theentire surface of the resulting structure, a gate insulating layer 408is provided. On the gate insulating layer 408, a gate electrode 409 isprovided in an area corresponding to the semiconductor layer 407 of thescanning TFT 103 and driving TFT 105. The gate electrode 409 of thedriving TFT 105 extends to the storage capacitor 104 as shown in FIG. 16and also serves as the lower electrode of the storage capacitor 104.

On the entire surface of the gate electrode 409, an interlayerinsulating layer 410 is provided. In the parts corresponding to thesource and drain regions of the semiconductor layer 407 of the scanningTFT 103 and driving TFT 105, in-element contact sections 413 areprovided in such a manner that they go through the gate insulating layer408 and interlayer insulating layer 410. Furthermore, in the partscorresponding to the gate electrodes 409 of the scanning TFT 103 anddriving TFT 105, the in-element contact sections 413 are provided insuch a manner that they go through the interlayer insulating layer 410.

Then, via the in-element contact sections 413, there is provided anin-element wire 411 a which connects one of the source and drain regionsof the scanning TFT 103 to the gate electrode 409 of the driving TFT105. Furthermore, via the in-element contact section 413, there areprovided an in-element wire 411 b that connects the gate electrode 409of the scanning TFT 103 to the scanning line 102, an in-element wire 411c that connects one of the source and drain regions of the driving TFT105 to the pixel electrode 201, an in-element wire 411 d that connectsthe other of the source and drain regions of the driving TFT 105 to thepower supply line 107, and an in-element wire 411 e that connects theother of the source and drain regions of the scanning TFT 103 to thesignal line 101. The in-element wire 411 d also serves as the upperelectrode of the storage capacitor 104.

A passivation layer 412 is provided on the in-element wires 411 a to 411e so as to cover all the elements above the buffer layer 406. In thepassivation layer 412 corresponding to a specific area of eachin-element wire 411 b to 411 e, a contact hole of the contact section108 is made.

On the passivation layer 412, a protective layer 414 is provided so asto cover not only the top but also the side of the layer 412. In thearea where the contact sections have been provided, the protective layer414 is also patterned to make openings for the contact sections 108.

Next, using FIGS. 15 to 17, the region above the element 301 and theregion excluding the element 301 in a single pixel will be explained.

A post-transfer insulating layer 415 is provided directly on theprotective layer 414 of the element 301 and on the final substrate 401in the region excluding the element 301 in the single pixel. In thepost-transfer insulating layer 415 in the regions corresponding to thespecific regions of the in-element wires 411 b, 411 c, 411 d, and 411 e,contact holes for the contact sections 108 are made respectively. Then,on the post-transfer insulating layer 415, the scanning line 102 thatconnects to the in-element wire 411 b, the pixel electrode 201 thatconnects to the in-element wire 411 c, the power supply line 107 thatconnects the in-element wire 411 d, and the signal line 101 thatconnects to the in-element wire 411 e are provided via these contactsections 108. On the pixel electrode 201, the organic EL section 106 isprovided. The organic EL section 106 is constructed by stacking a holeinjection layer, a light-emitting layer, and a cathode one on top ofanother in this order.

Next, a method of manufacturing EL displays with the above-describedconfiguration according to the second embodiment will be explained.

In the EL display manufacturing method of the second embodiment,elements 301 as shown in FIGS. 16 and 17 are formed on an elementformation substrate. Then, they are transferred to an intermediatesubstrate and further to a final substrate. Thereafter, interconnectionsare formed.

An alkali-free glass substrate is used as the element formationsubstrate (not shown). On the entire surface of the element formationsubstrate, an under layer (etching stopper layer) 405 that makes elementseparation easy is formed. A material having hydrofluoric acidresistance, such as aluminum (AlOx), TaOx, SiNx, Si, etc. of about 1 to2 μm is used for the under layer 405. Then, on the entire surface of theunder layer 405, a layer of SiNx, SiOx, etc. is formed to a thickness ofabout 200 nm to 2 μm as the buffer layer 406.

On the entire surface of the buffer layer 406, an amorphous siliconsemiconductor layer 407 is deposited to a thickness of about 50 nm byCVD techniques. The amorphous silicon semiconductor layer 407 is heatedrapidly and crystallized, thereby forming a polycrystalline siliconlayer 407. The polycrystalline silicon layer 407 is so processed byphotolithography that it takes the form of islands, thereby forming asemiconductor layer 407 of a scanning TFT 103 and a driving TFT 105.

Next, an SiO₂ layer is formed as a gate insulating layer 408 on theentire surface by CVD techniques to a thickness of about 150 nm. On thegate insulating layer 408, MoW is sputtered to form a layer about 400 nmthick. The MoW layer is processed by photo-lithography, thereby formingthe gate electrodes 409 of the scanning TFT 103 and driving TFT 105. Thegate electrode 409 of the driving TFT 105 also serves as the lowerelectrode of the storage capacitor 104.

With the gate electrode 409 as a mask, doping is done by implantingimpurity ions or by an ion shower, thereby forming the source and drainregions of the scanning TFT 103 and driving TFT 105. In forming thesource and drain regions, LDD (Lightly Doped Drain) regions may beformed. In forming the LDD regions, after a mask that covers the LDDregions with resist is provided and impurity ions are implanted with ahigh dose, the resist is removed and then impurity ions are implantedwith a low dose.

Since in the second embodiment, both of the scanning TFT 103 and drivingTFT 105 may be composed of n-type TFTs, phosphorus is doped in thesource and drain regions so as to achieve about 10²⁰ cm⁻³. These TFTsmay be realized by p-type TFTs or a CMOS structure. In the case of CMOS,n-type and p-type impurities, such as phosphorus and boron, are doped insequence. When one type of impurity is doped, the TFTs not to be dopedare covered.

Next, an SiO₂ layer is formed by plasma CVD techniques to a thickness ofabout 400 nm, which produces an interlayer insulating layer 410.Openings are made by photolithography in specific areas of the gateinsulating layer 408 and interlayer insulating layer 410 correspondingto the source and drain regions of the semiconductor layer 407 of thescanning TFT 103 and driving TFT 105, thereby making contact holes forthe in-element contact sections 413.

Furthermore, openings are made by photolithography in specific areas ofthe interlayer insulating layer 410 corresponding to the gate electrodes409 of scanning TFT 103 and driving TFT 105, thereby making contactholes for the in-element contact sections 413.

Next, an Al alloy, such as Al—Zr, is deposited by sputtering techniquesto a thickness of about 500 to 800 nm. The resulting layer is patternedby photolithography, thereby forming in-element wires 411 a to 411 e.

Since the in-element wires 411 a to 411 e are to be connected to otherelectrodes at the contact section 108 later, if they keep having theAl-alloy surface, an oxide layer appears, which might increase thecontact resistance. Therefore, an Mo layer may be formed on the Al alloyto make oxidation less likely or give conductivity to the wires evenafter they are oxidized.

It is desirable that the areas of the in-element wires 411 to make thecontact sections 108 should be improved in chemical resistance. Toachieve this, it is desirable that at least the areas to make thecontact sections 108 should be made of refractory metal, such as MO, W,or Ta, a noble metal, such as Pt or Au, a metal, such as Cu or Ni, or analloy of Cu or Ni.

The in-element wire 411 a connects one of the source and drain regionsof the scanning TFT 103 to the gate electrode 409 of the driving TFT 105via the in-element contact section 413. The gate electrode 409 of thescanning TFT 103 is connected to the scanning line 102 via thein-element contact section 413. One of the source and drain regions ofthe driving TFT 105 is connected to the pixel electrode 201 via thein-element contact section 413. The other of the source and drainregions of the driving TFT 105 is connected to the power supply line 107via the in-element contact section 413. The other of the source anddrain regions of the scanning TFT 103 is connected to the signal line101. The scanning line 102, pixel electrode 201 (not shown), powersupply line 107, and signal line 101 are formed above the in-elementwires 411 a to 411 e. A method of forming them will be explained later.

Next, to separate the individual elements on the element formationsubstrate into island-like pieces, the interlayer insulating layer 410,gate insulating layer 408, and buffer layer 406 in the periphery of eachelement are patterned by RIE techniques or the like.

A passivation layer 412 is formed using SiNx by CVD (Chemical VaporDeposition) techniques in such a manner that the layer 412 covers eachof the separated elements. The region of the passivation layer 412corresponding to the contact section 108 and the peripheral region ofeach element 301 are removed. Then, a protective layer 414 is formedusing the same AlOx as that of the under layer 405 in such a manner thatthe layer 414 further covers the regions covered with the passivationlayer 412. The regions of the protective layer 414 corresponding to thecontact sections 108 and the peripheral region of each element 301 areremoved.

In the second embodiment, the passivation layer 412 is formed using SiNxwhose water permeability is low. In addition, the under layer 405 andprotective layer 414 are so formed using AIOx that they cover all theelements. With this configuration, damage to the elements in thetransfer process is reduced, the curving of the elements is preventedowing to stress relaxation, contamination from outside the elementsincluding the adhesive is prevented, and the reliability of the elementsin terms of water resistance is improved.

The protective layer 414 and passivation layer 412 may be made of thesame material, which enables the protective layer 414 to also serve as apassivation layer. In that case, to produce the above effect, a stackedlayer of AlOx and SiNx, or AlSiNxOy and TaOx, or the like may be used.

In the method of making the opening sections 108 in the passivationlayer 412 and protective layer 414, a post-transfer insulating layer maybe formed after the process of transferring the elements to the finalsubstrate explained later and thereafter these three layers may bepatterned simultaneously. In this case, although a protective layercannot be formed so as to cover the passivation layer on the sides ofthe elements, the adverse effect can be minimized by making suitablemodifications to the process of taking the elements out of the elementformation substrate.

Furthermore, after the passivation layer 412 is formed, a protectivelayer 414 may be formed without separating the elements and thereafterthe elements may be separated. In that case, to increase thereliability, it is desirable that the scanning TFT 103 and driving TFT105 should be separated about 5 to 10 μm away from the end in separatingthe elements. When the elements are separated, the under layer 405 maynot be separated.

Since the process of transferring the elements thus formed on theelement formation substrate to the intermediate substrate and further tothe final substrate on which the height control members and the adhesivesurrounded by the height control members have been formed is carried outby the method described in the first embodiment, an explanation of theprocess will be omitted.

Next, as shown in FIG. 17, on the entire surface of the final substrate401 to which the elements 301 have been transferred, a post-transferinsulating layer 415 is formed using photosensitive acrylic resin. Thepost-transfer insulating layer 415 corresponding to the contact sections108 of the elements 301 is removed, thereby forming opening sections.

Next, as shown in FIG. 15, Al, ITO, or the like is formed on the entiresurface by sputtering techniques or the like. The resulting layer ispatterned by photolithography or the like, thereby forming a signal line101, a scanning line 102, a power supply line 107, and a pixel electrode201.

Thereafter, as shown in FIG. 15, an organic EL section 106 is providedon the pixel electrode 201. The resulting structure is laminated with acover substrate and sealed. Then, wiring is done (not shown), whichcompletes an EL display.

Furthermore, an opposite substrate on which transparent electrodes andothers have been formed may be caused to face the final substrate onwhich the elements have been formed. Then, liquid crystal is injectedbetween them. Then, the resulting structure is sealed and wired, whichcompletes the liquid-crystal display.

In the second embodiment, such elements are transferred to the finalsubstrate on which the height control members and the adhesive have beenformed, thereby forming an EL display with the height-controlledelements. Since the height of the elements has been controlled, there isno variation in the capacitances developed between the wires and theelements, which assures a high display quality.

Furthermore, in the second embodiment, since the size of one pixel isset to about 40 μm×about 120 μm and the size of one element is set toabout 40 μm×about 25 μm, as shown in FIG. 15, the size of the element isabout ⅕ of that of a pixel. The manufacture of elements requires manyprocessing steps. In the second embodiment, elements are formed withhigh density using a special element formation substrate and thentransferred. Therefore, when the element formation substrate is as largeas the final substrate, as many elements as there are on four or morefinal substrates can be formed on a single element formation substrate.Since elements requiring many manufacturing processes can be formed at atime, this helps reduce the cost, which is desirable.

In the second embodiment, each element is provided on the under layerwhich has been separated element by element. The under layer mitigatesstrain in the lower part of the element, which increases reliability.The mitigation of strain prevents the characteristics of the elementsfrom changing and further avoids detachment failure, which helps improvethe reliability of adhesion during transfer.

Furthermore, while in the second embodiment, photosensitive acrylicresin has been used as the height control members of the adhesion part,the height control members are not limited to this material and may beanother solid material, provided that it can maintain the height of theadhesion part. For instance, since the following materials can controlthe height of the adhesion part, they are desirable materials for theheight control members: photosensitive resin, such as polyimide, BCB(benzocyclo-butene) or, fluoric resin, nonphotosensitive resin, such asPET (polyethylene telephtalate), PES (polyether sulfone), or PEN(polyethylene naphtalate), which is used as a substrate, or a processingmaterial for embossing a substrate or injection-molding a substrate, andinorganic insulating layers, such as an SiOx layer formed by calcining acoating-type SOG (Spin On Glass) or a layer of polysilazane, SiOx, SiNx,or phosphorous glass formed by CVD techniques.

While in the embodiment, ultraviolet-curing adhesive has been used asthe adhesive of the adhesion part, the adhesive is not restricted tothis and may be another adhesive, provided that it adheres to theelements when the active matrix substrate is completed. For instance,since thermosetting adhesive, thermoplastic adhesive, elastic adhesive,and alloy adhesive adhere well to the elements, they are desirablematerials.

Materials for these adhesives include, for instance, one-part epoxyresin, two-part epoxy resin, acrylic resin, melamine resin, polyimideresin, polyester resin, polybenzimidazole resin, phenolic resin, urearesin, resorcinol resin, cellulose acetate resin, nitrocellulose resin,polyvinyl acetate resin, polyvinyliden chloride resin, polyamide,cyanoacrylate, polyurethane rubber, silicone rubber, and acrylicemulsion.

These adhesives may be liquid when being formed and hardened later. Theymay be applied by a method of dropping a specific amount from a nozzleor ink-jet. To drop adhesive, a mechanical pump or a piezoelectricdevice may be used for dispensing adhesive or propelling drops ofadhesive through the air. Moreover, a solid adhesive may be segmentedinto small pieces at the time of the formation of adhesive. The smallpieces are arranged mechanically or attracted by electrostatic force forarrangement. Since the adhesive does not control the height, it may be asolid that has plasticity or elasticity.

While in the second embodiment, a glass substrate has been used as thefinal substrate, a plastic substrate, resin film, ceramic substrate,thin metal sheet substrate, or the like may be used as the finalsubstrate. Previously, although a plastic substrate, resin film, or thelike was light, they could not be formed accurately into ahigh-precision active matrix substrate because the thermal deformationand thermal expansion coefficient were large. In the second embodiment,however, the formation of elements including heating processes iscarried out on the element formation substrate and the resultingelements are transferred. This enables lightweight substrates to beselected, regardless of the material of the final substrate.

Next, FIG. 18 shows a modification of the process of transferring theelements from the intermediate substrate to the final substrate in thefirst or second embodiment. In FIG. 18, the same parts as those in thefirst embodiment are indicated by the same reference numerals and anexplanation of them will be omitted.

In this modification, as shown in FIG. 18, an on-intermediate-substratemask 1701 is further provided in such a manner that it is in contactwith the intermediate substrate 601. When the intermediate substrate 601is thick, if light is projected only through a glass mask 1201, thelight might be projected onto the unselected elements 301. Providing theon-intermediate-substrate mask 1701 makes the boundary of the lightprojecting area clear, which improves the selectivity of the elements301 to be transferred.

In the case of this modification, even if an optical conversion materialis not provided, the selectivity is improved. Therefore, this isparticularly effective in using a temporary adhesion layer 603 whoseadhesion decreases due to ultraviolet rays or when unable to find asuitable material for an optical conversion material. This modificationis also effective when the elements 301 to be transferred are as smallas about 20 to 40 μm, because the temporary adhesion layer 603 can bepeeled with a high space precision.

In this modification, too, since the adhesion part 404 selectively bondsonly one element 301 to the adhesive 301 and height control member 402,the element 301 is bonded to the adhesion part 404 and peeled from thetemporary layer 603, which assures a comprehensive selectivity.

Either the glass mask 1201 or on-intermediate-substrate mask 1701 may beomitted and a laser beam may be used. Then, the laser beam is projectedonto only the elements 301 to be transferred.

Next, examples of the shape of the adhesion part formed on the finalsubstrate differing from that in the first (or second) embodiment willbe explained in a third to a ninth embodiment of the present invention.In these embodiments, because the parts excluding the adhesion parts areformed as in the first embodiment, an explanation of the parts excludingthe adhesion parts will be omitted.

Third Embodiment

FIG. 19A is a sectional view of an element in an active matrix substrateaccording to a third embodiment of the present invention. FIG. 19B is aplan view of an adhesion part corresponding to one element. As shown inFIG. 19B, the third embodiment has the same configuration as the firstembodiment except that the inside of the height control member 402 ofthe adhesion part 404 takes the form of a circle. The broken line inFIG. 19B shows the outside of the element 301.

In the third embodiment, the inside of the height control member 402 iscaused to have a curved surface with a specific curvature, which reducesthe gap between the spread adhesive 403 and the height control member402 when the element 301 is pressed against the adhesion part 404. Whena liquid adhesive with high viscosity is used as the adhesive 403, thisparticularly produces a great effect, because the shape produced as aresult of being pressed by the element 301 would take the form of acurved surface.

When the outside of the height control member 402 has a form similar toa regular square, it is desirable that its inside should be madecircular. If the inside of the height control member 402 has a curvedsurface with the curvature corresponding to the shape of the outside ofthe height control member 402, a similar effect can be obtained.Although the radius of curvature of the inside of the height controlmember 402 depends on the viscosity of the material for the adhesive 403or the like, it should be about ⅕ to ½ of the length of one side of theheight control member 402. The material and the forming method for theheight control member 402 are the same as in the first embodiment.

Fourth Embodiment

FIG. 20A is a sectional view of an element formed in an active matrixsubstrate according to a fourth embodiment of the present invention.FIG. 20B is a plan view of an adhesion part corresponding to oneelement. FIG. 20C is a plan view of one element. As shown in FIG. 20B,the fourth embodiment has the same configuration as the first embodimentexcept that the height control member 402 of the adhesion part 404 is soformed that it has a cut 1901 in it and encloses the adhesive 403. Thebroken line in FIG. 20B shows the outside of the element 301.

In the fourth embodiment, since the height control member 402 isprovided in such a manner that it has a cut in it and encloses theadhesive 403, even when the amount of adhesive 403 is a little too much,extra adhesive 403 flows through the cut 1901 to the outside of theheight control member 402. Therefore, even if the amount of adhesive 403is not controlled precisely, the height and spread of the adhesion part404 can be controlled.

Furthermore, when the cut 1901 is so made that it is narrower at thepart near the inside of the height control member 402 and wider at thepart near the outside, the height of the adhesive that flows from thecut 1901 is less than the height of the height control member 402, whichprevents the adhesion from adhesive to adjacent elements.

Moreover, when the cut 1901 is made in a different or separate positionfrom the position corresponding to the contact section 108 of theelement 301 as shown in FIG. 20C, even if the adhesive flows from thecut 1901 and extends over the element 301, the occurrence of poorcontact can be reduced.

The cut 1901 may be a hole made in the sidewall of the height controlmember.

Fifth Embodiment

FIG. 21A is a sectional view of an element formed in an active matrixsubstrate according to a fifth embodiment of the present invention. FIG.21B is a plan view of an adhesion part corresponding to one element. Thearea shown by a broken line in FIG. 21B is the position corresponding toan element 301. As shown in FIG. 21B, the fifth embodiment has the sameconfiguration as the first embodiment except that the element 301 isprovided inside the height control member 402 of the adhesion part 404.

In the fifth embodiment, when the elements 301 are transferred from theintermediate substrate to the final substrate, the temporary adhesionlayer around the element 301 comes in contact with the height controlmember 402 to prevent the element from being pressed any further (FIG.21), which keeps the height of the adhesion part 404 constant as in thefirst embodiment and enables the element to be transferred in such amanner that the element is almost parallel to the surface of the finalsubstrate. Furthermore, since the height can be controlled, the adhesive403 can be prevented from spreading. In the fifth embodiment, providingthe element 301 inside the height control member 402 increases thecontact area of the element 301 and adhesive 403, resulting in anincrease in adhesion.

The fifth embodiment cannot be applied to a case where the transfer ofthe element to the immediate substrate 601 is carried out by bonding theelement to the adhesion layer 603 a as shown in FIG. 3D, because theelement 301 is not buried in the temporary adhesion layer in such amanner that the element is flush with the surface.

Sixth Embodiment

FIG. 22A is a sectional view of an element formed in an active matrixsubstrate according to a sixth embodiment of the present invention. FIG.22B is a plan view of an adhesion part corresponding to one element. Asshown in FIG. 22B, the sixth embodiment has the same configuration asthe first embodiment except that not only is the height control member402 of the adhesion part 404 so provided that it encloses the adhesive403, but also a second height control member 2101 is provided under theelement 301 region.

In the sixth embodiment, the second height control member 2101 is formedby photolithography using photosensitive acrylic resin, such as OPTMERfrom JSR Corporation, epoxy resin, or novolac resin. The height controlmember 402 and second height control member 3101 may be formedsimultaneously. For instance, photosensitive acrylic resin is formed onthe entire surface. Then, with a photo mask corresponding to the heightcontrol member 402 and second height control member 2101, exposure anddevelopment are carried out, thereby producing two control members withthe same height.

In the sixth embodiment, providing the second height control member 2101also under the region corresponding to the element 301 enables theheight of the element 301 to be controlled precisely. This feature isparticularly effective in making the element 301 smaller than the innercircumference of the height control member, as shown by dotted lines inFIGS. 22A and 22B. It is desirable that the total cross-sectional areaof the second height control member 2101 provided under the element 301region should be about 0.1 to 0.8 times the area of the element 301.When the element 301 has a low strength against deformation, it isdesirable that the area of the second height control member 2101 shouldbe as large as possible in order to reduce damage to the element.Particularly when the area to be transferred at a time is large and thepressure at which the intermediate substrate 601 and final substrate 401are pressed varies from place to place, it is desirable that the areashould be about 0.5 or more times the area of the element 301 to reducedamage to the element 301.

Seventh Embodiment

FIG. 23A is a sectional view of an element formed in an active matrixsubstrate according to a seventh embodiment of the present invention.FIG. 23B is a plan view of an adhesion part corresponding to oneelement. As shown in FIG. 23B, the seventh embodiment has the sameconfiguration as the first embodiment except that the height controlmember 402 of the adhesion part 404 is not provided so as to surroundthe adhesive 403 and the adhesive 403 surrounds the height controlmember 402.

In the seventh embodiment, a plurality of small height control members402 are formed by patterning so as to stand side by side. As for theadhesive 403, a material capable of keeping its shape at the time offormation is formed into a specific shape by printing or the like. It isdesirable that the outward shape of the adhesive 403 should be similarto that of the element 301.

In the seventh embodiment, although the height control member 402 is notprovided so as to surround the adhesive 403, use of the height controlmember 402 keeps the height constant even when the element 301 ispressed as explained in the other embodiments.

Since the adhesive 403 itself keeps its shape and the height controlmember 402 restrains the element 301 from being pressed, the adhesive403 is prevented from spreading. A material capable of being formed byprinting or the like and keeping its shape by itself includes aliquid-crystal main seal adhesive where thickening agent or the like ismixed, such as printing ink, ultraviolet-curing epoxy resin,thermosetting epoxy resin, and acrylic resin.

Eight Embodiment

FIG. 24A is a sectional view of an element formed in an active matrixsubstrate according to an eighth embodiment of the present invention.FIG. 24B is a plan view of an adhesion part corresponding to oneelement. As shown in FIG. 24B, the eighth embodiment has the sameconfiguration as the first embodiment except that the height controlmembers 402 of the adhesion part 404 are not provided so as to surroundthe adhesive 403 and the height control members 402 are distributed inthe adhesive 403.

In the eighth embodiment, the adhesion part 404 is formed by printing insuch a manner that the height control members 402 are distributed in theadhesive 403. As for the height control members 402, silica, SiNx,polyester, polyethylene, acrylic resin, or the like is formed intopillar-like pieces, sphere-like pieces, fiber-like pieces, bead-likepieces, or pieces of another shape. Then, these pieces are distributedin the adhesive 403 singly or in a mixed manner.

In the eighth embodiment, too, use of the height control members 402makes the height of the element 301 constant even when the element 301is pressed and prevents the adhesive 403 from spreading as in the otherembodiments. Furthermore, since the eighth embodiment does not includethe process of forming the height control members 402, it has the effectof decreasing the number of active matrix manufacturing steps.

Ninth Embodiment

FIG. 25A is a sectional view of an element formed in an active matrixsubstrate according to a ninth embodiment of the present invention. FIG.25B is a plan view of an adhesion part corresponding to one element. Asshown in FIG. 25B, the ninth embodiment has the same configuration asthe first embodiment except that the height control member 402 of theadhesion part 404 surrounds not only the adhesive 403 but also a part ofthe top of the adhesive 403. In FIG. 25B, the broken line indicates theoutside of the element 301.

In the ninth embodiment, an adhesive 403 is first formed by printing orthe like. Then, a height control member 402 previously formed usingplastic is bonded to the final substrate 401. Thereafter, as in theother embodiments, the element 301 is pressed against the height controlmember 402, thereby bonding the element 301 to the adhesive 403 stickingout from the top surface of the height control member 402.

In the ninth embodiment, even when the element 301 is pressed, theheight of the element 301 is kept constant and the adhesive 403 isprevented from spreading as in the other embodiments. Furthermore, inthe ninth embodiment, since the sides and part of the adhesive 403 arecovered with the height control member 402, a much greater margin can beleft in the adhesive applying process, which helps improve the yield inbonding the elements 301.

In addition, the above embodiments may be combined suitably.

As has been described above, with the present invention, it is possibleto provide an active matrix substrate which is capable of controllingthe height of active elements from the surface of the final substrate intransferring the active elements and enables the active elements to bealmost parallel to the final substrate even via an adhesion part. It isfurther possible to provide a method of manufacturing such active matrixsubstrates.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. An active matrix substrate comprising: a substrate; a plurality ofadhesion parts provided on said substrate having substantially the sameheight, each of said plurality of adhesion parts including an insulativeheight control member and an adhesive; and a plurality of activeelements each having at least one contact section on an upper surfacethereof, each having a bottom surface smaller in area than an uppersurface of said respective one of said plurality of adhesion parts, andeach being provided on a respective one of said plurality of adhesionparts such that the bottom surface thereof is provided inside theinsulative height control member of said respective one of saidplurality of adhesion parts.
 2. The active matrix substrate according toclaim 1, further comprising a plurality of insulating layers providedbetween said plurality of adhesion parts and said plurality of activeelements.
 3. The active matrix substrate according to claim 2, whereinsaid plurality of insulating layers include silicon nitride.
 4. Theactive matrix substrate according to claim 1, wherein each of saidplurality of adhesion parts includes, as said insulative height controlmember, a plurality of particles dispersed in said adhesive.
 5. Theactive matrix substrate according to claim 4, wherein said plurality ofparticles have at least one shape selected from the group consisting ofa sphere-like shape, a pillar-like shape, and a fiber-like shape.
 6. Theactive matrix substrate according to claim 1, wherein each of saidplurality of adhesion parts includes, as said insulative height controlmember, a plurality of pillar-like members standing side by side in saidadhesive, and said plurality of pillar-like members have substantiallythe same height.
 7. An active matrix substrate comprising: a substrate;a plurality of adhesion parts provided on said substrate havingsubstantially the same height, each of said plurality of adhesion partsincluding an insulative height control member and an adhesive; and aplurality of active elements each having at least one contact section onan upper surface thereof, wherein each of said plurality of activeelements is located inside the insulative height control member and isplaced on the adhesive, a bottom of each of said plurality of activeelements being smaller in area than an upper surface of the adhesive.